全文获取类型
收费全文 | 1464篇 |
免费 | 41篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 81篇 |
化学工业 | 389篇 |
金属工艺 | 31篇 |
机械仪表 | 31篇 |
建筑科学 | 26篇 |
能源动力 | 68篇 |
轻工业 | 117篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
无线电 | 129篇 |
一般工业技术 | 278篇 |
冶金工业 | 221篇 |
原子能技术 | 51篇 |
自动化技术 | 79篇 |
出版年
2023年 | 11篇 |
2022年 | 46篇 |
2021年 | 46篇 |
2020年 | 20篇 |
2019年 | 28篇 |
2018年 | 31篇 |
2017年 | 32篇 |
2016年 | 41篇 |
2015年 | 25篇 |
2014年 | 59篇 |
2013年 | 91篇 |
2012年 | 79篇 |
2011年 | 80篇 |
2010年 | 63篇 |
2009年 | 60篇 |
2008年 | 70篇 |
2007年 | 55篇 |
2006年 | 52篇 |
2005年 | 40篇 |
2004年 | 36篇 |
2003年 | 43篇 |
2002年 | 29篇 |
2001年 | 29篇 |
2000年 | 20篇 |
1999年 | 19篇 |
1998年 | 83篇 |
1997年 | 49篇 |
1996年 | 48篇 |
1995年 | 31篇 |
1994年 | 19篇 |
1993年 | 23篇 |
1992年 | 8篇 |
1991年 | 14篇 |
1990年 | 20篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 11篇 |
1982年 | 3篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有1510条查询结果,搜索用时 15 毫秒
211.
212.
High‐fat Diet‐induced Intestinal Hyperpermeability is Associated with Increased Bile Acids in the Large Intestine of Mice 下载免费PDF全文
Metabolic syndrome is characterized by low‐grade chronic systemic inflammation, which is associated with intestinal hyperpermeability. This study examined the effects of 3 high‐fat diets (HFDs) composed of different fat sources (soybean oil and lard) on the intestinal permeability, tight junction (TJ) protein expression, and cecal bile acid (BA) concentrations in mice, and then analyzed their interrelations. C57/BL6 mice were fed the control diet, HFD (soybean oil), HFD (lard), and HFD (mix; containing equal concentrations of soybean oil and lard) for 8 wk. Glucose tolerance, intestinal permeability, TJ protein expression, and cecal BA concentration were evaluated. Feeding with the 3 HDFs similarly increased body weight, liver weight, and fat pad weight, and induced glucose intolerance and intestinal hyperpermeability. The expression of TJ proteins, zonula occludens‐2 and junctional adhesion molecule‐A, were lower in the colons of the 3 HFD groups than in the control group (P < 0.05), and these changes appeared to be related to intestinal hyperpermeability. Feeding with HFDs increased total secondary BA (SBA) and total BA concentrations along with increases in some individual BAs in the cecum. Significant positive correlations between intestinal permeability and the concentrations of most SBAs, such as deoxycholic acid and ω‐muricholic acids, were detected (P < 0.05). These results suggest that the HFD‐induced intestinal hyperpermeability is associated with increased BA secretion. The abundance of SBAs in the large intestine may be responsible for the hyperpermeability. 相似文献
213.
Akio Katsuki Hiromichi Onikura Takao Sajima Satoshi Machida Kazuhiro Oda 《Precision Engineering》1994,16(4):296-301
A laser-guided BTA tool has been developed to prevent axial hole deviations. Four kinds of experiments were conducted to examine the performance of this tool in detail and to determine its practical application using a duralumin (A2017-T4) workpiece with a prebored 108-mm diameter hole. The first experiment was performed to examine the conditions of the hole deviation in the case of normal deep-hole boring. The second was to examine whether the tool corrects for the stated hole deviation. The third was to examine whether the tool can go straight through to the target without shifting toward a thin wall (t = 0.7 mm) on one side of the workpiece. The fourth was to examine whether the tool can be guided toward the target without affecting a prebored hole, which was inclined to radial direction at 100 μm for a hole length of 100 mm. The experiments were performed with a rotating tool-stationary workpiece system. Rotational speed was 270 rpm and feed ws 0.125 mm/rev. Tool diameter was 110 mm. The results show that the tool can be guided to go straight through toward the target despite the disturbances. 相似文献
214.
Takafumi Ishii Takuya Maie Naofumi Kimura Yuki Kobori Yasuo Imashiro Jun-ichi Ozaki 《International Journal of Hydrogen Energy》2017,42(23):15489-15496
The use of carbon cathode catalysts in polymer electrolyte fuel cells instead of the current platinum catalysts is attracting increasing attention. We claim that two factors are important for enhancing the activity of carbon cathode catalysts in the oxygen reduction reaction (ORR): the formation of a nanoshell structure and co-doping with boron and nitrogen. Herein, we investigate the preparation and characterization of active ORR carbon catalysts that combine the above factors. Boron and nitrogen (BN)-doped nanoshell-containing carbon (BN-NSCC) was prepared by carbonizing a mixture of poly(furfuryl alcohol), cobalt phthalocyanine, melamine, and a trifluoroborane–methanol complex at 1000 °C. Transmission electron microscopy and X-ray photoelectron spectroscopy revealed the formation of nanoshell structures with distorted graphitic layers and the introduction of boron and nitrogen atoms, respectively. The ORR activity was evaluated in oxygen-saturated 0.5 mol dm?3 H2SO4 using Koutecky–Levich analysis. The BN-NSCC showed an eight to ten times higher ORR activity than undoped NSCC, with an increased number of electrons participating in the reaction. Tafel analysis revealed a change in the rate-determining step caused by BN-doping. Thus, the combination of a nanoshell structure and co-doping with boron and nitrogen was found to improve the ORR activity of carbon catalysts. 相似文献
215.
216.
We investigated the diffusion process of H2O2 generated during O2 reduction at a Pt microdisk electrode used as a generator for scanning electrochemical microscopy (SECM). First, the amount of O2 consumption and generated H2O2 at the Pt generator electrode are estimated using a detector electrode installed in the SECM. Based on the results, a large amount of O2 consumption and generated H2O2 are detected at the center of each generator electrode. According to the measurement, the O2 starvation and H2O2 detection currents can be defined. Subsequently, the O2 starvation and H2O2 detection currents are measured by varying the generator size. As a result, these currents decrease with a decrease in the generator electrode size, however, the H2O2 diffusion process is changed for the generator diameter of less than 50 μm. Finally, the O2 starvation and H2O2 detection measurements were conducted using a Nafion-coated Pt microdisk electrode. The amount of O2 consumption is not suppressed, while the amount of generated H2O2 decreases with the Nafion layer prepared on the Pt electrode. This result indicates that the thickness of the H2O2 diffusion layer in the H2SO4 solution is dramatically diminished by coating the Nafion layer on the Pt generator. 相似文献
217.
218.
Makoto Shiota Toshiaki Uchida Taishi Oda Hiroshi Kawakami 《Journal of food science》2006,71(3):C120-C123
ABSTRACT: We investigated the oxidative stability of soybean oil and fish oil fortified with iron solubilized by lactoferrin (FeLF). Oxidative stability was evaluated by measuring the induction period of the Rancimat test. The induction time of soybean oil added FeCl3 was decreased; however, that of added FeLF was not. This effect of lactoferrin was also observed in the iron-catalyzed oxidation offish oil at temperatures ranging from 50°C to 120°C, and at concentrations of iron ranging from 0 to 500 ppm. Thus, lactoferrin is considered useful as a natural iron stabilizer for food products containing polyunsaturated fatty acids. 相似文献
219.
220.
Natsui Shungo Sudo Takuya Shibuya Ryota Nogami Hiroshi Kikuchi Tatsuya Suzuki Ryosuke O. 《Metallurgical and Materials Transactions B》2020,51(1):11-15
Metallurgical and Materials Transactions B - An in situ observation technique of the TiO2 interfacial behavior in molten LiCl-KCl electrolysis was developed. The variation of the thin TiO2... 相似文献